Divide a round room by constructing a straight wall through its center, creating two semi-circular rooms. Although these rooms will have a very different feel from one large round room, they do provide the advantage of one straight wall against which you can put large furniture.
Build more curved walls within the cornerless room to create smaller rooms of various shapes. By constructing arch shaped walls that run through the center point of the room, you can create several smaller, seed-shaped rooms with irregularly shaped closets in between them.
Divide a round or oval room into three identical smaller rooms by building three radial walls that meet in the center of the original room. You will then have three rooms, each of which is shaped like a slice of pie.